Harrison was selected to attend the Armed Forces Staff College with subsequent assignment and promotion to lieutenant colonel, as the "ground guy" in the Southeast Asia Division of J-5, CINCPAC Headquarters, Hawaii. After six months in this joint assignment, Major General George P. Seneff, commanding officer of the 1st Aviation Brigade, USARV, requested Harrison's assignment to command a combat aviation battalion. In Vietnam, Colonel Harrison was given command of the 10th Combat Aviation Battalion during his first tour of duty, in 1966-67. (He was the only officer to command a separate combat aviation battalion for a full year during the entire Vietnam War). Continuing his commitment to the airmobility concept in his leadership and training emphasis, the battalion's combat operations involved night operations and instrument flying. After Vietnam, he was assigned to the Office of the Secretary of Defense (OSD) in Robert McNamara's four-officer Training Division where he conducted a study of operational flight training for fighter pilots in the Navy, Air force and Marines. A one-year tour in OSD and then to the Air War College, promotion to colonel, and back to Washington as Chief of the Doctrine Division in the Office of the Assistant Chief of Staff for Force Development. At the request of Maj Gen John Wright, commanding general of the 101st Airborne Division, and after only one year in the Pentagon, Harrison returned to Vietnam in 1970, where he commanded the 3d Brigade of the 101st Airborne Division (Airmobile). The 101st was the only full-strength division in Vietnam at this time, although not at full Table of Organization and Equipment (TO&E) strength. As such and strategically located in the northern portion of South Vietnam near the DMZ, the A Shau Valley and Laos, the 101st was selected to conduct the only offensive campaign launched by General Creighton Abrams, COMUSMACV in 1970, with the mission of destroying as much of the stocks and bases of the North Vietnamese Army in this area as a "final" major assist to the Vietnamization of the war process as all US combat troops were withdrawing from Vietnam. The 3rd Brigade was selected to lead this offensive by establishing a base near the Ashau from which attacks could be launched. From the start of planning, the then brigade commander, Col Bill Bradley and his Operations Officer, Maj Tex Turner, requested significant augmentation of the brigade to operate in this area. None was